Time Zone Converter — World Clock & Meeting Planner

Convert times between any of 400+ time zones instantly. Compare multiple cities side by side, find the best meeting time across zones, and see DST change dates for every region.

Popular Pairs

Source Time

Date & Time

Source Timezone

New York (US Eastern) — GMT-4

Tue, Apr 28, 12:50 PM

Target Timezones (2/5)

Target 1

London — GMT+1

Tue, Apr 28, 05:50 PM

Target 2

Tokyo (JST) — GMT+9

Wed, Apr 29, 01:50 AM

UTC Offsets at Selected Time

New York (US Eastern)

GMT-4

Source

London

GMT+1

Target 1

Tokyo (JST)

GMT+9

Target 2

What Is the Time Zone Converter — World Clock & Meeting Planner?

This converter translates any date and time across up to five target time zones simultaneously, using JavaScript's built-in Intl.DateTimeFormat API — no external libraries, no network requests. It handles DST automatically for all IANA-compliant time zones.

›Multi-zone comparison — add up to five target zones and see the converted time for each, updated instantly as you change the source.
›World Clock mode — shows the live current time in every added zone, updating every second via a real-time clock.
›Meeting Planner — highlight business-hours overlap (9 am–5 pm) across zones with green/yellow/red colour coding so you can find the best meeting window.
›DST awareness — displays the next DST transition date and offset change for each zone so you can plan around clock changes.
›Popular presets — one-click presets for common international meeting pairs like NYC/London and NYC/Tokyo save setup time.

Formula

Time Zone Conversion

Target Time = Source Time + (Target UTC Offset − Source UTC Offset)

UTC Offset

UTC Offset = Standard Offset ± DST Adjustment (0 or +1 hour)

JavaScript API Used

new Intl.DateTimeFormat("en-US", { timeZone: tz }).format(date)

Term	Meaning	Example
UTC	Coordinated Universal Time	The reference point from which all offsets are measured
UTC Offset	Hours from UTC	UTC+5:30 = India Standard Time, 5 hours 30 min ahead
DST	Daylight Saving Time	Clocks move +1 hour in spring, −1 hour in autumn
IANA TZ	IANA timezone identifier	"America/New_York", "Europe/London", "Asia/Tokyo"
Offset Δ	Difference between zones	NYC (UTC−5) to Tokyo (UTC+9) = 14 hours ahead

How to Use

1
Set source time: Enter a date and time in the source fields, or click "Now" to use the current moment.
2
Choose source timezone: Search for a city or region from the dropdown. The list covers 50+ major zones across all continents.
3
Add target timezones: Click "Add Timezone" to add one or more target zones (up to five). Search by city or region name.
4
Read converted times: Converted times appear instantly for each target zone, including the UTC offset and date (in case of a day boundary crossing).
5
Use Meeting Planner: Toggle Meeting Planner to see which hours overlap with standard business hours (9 am–5 pm) in each zone, colour-coded green/yellow/red.
6
Enable World Clock: Toggle World Clock mode to see live, auto-updating current times for all zones — useful as a reference while you work.
7
Try a preset: Click any "Popular Pairs" preset to instantly load a common international pairing like NYC/London or London/Singapore.

Example Calculation

Converting a 2 pm Tuesday meeting from New York to London, Dubai, and Tokyo

Source: 2026-04-21 14:00 — America/New_York (UTC−4, EDT)

Europe/London (UTC+1, BST): 19:00 Tue Apr 21

Asia/Dubai (UTC+4): 22:00 Tue Apr 21

Asia/Tokyo (UTC+9): 03:00 Wed Apr 22 ← next day

Meeting Planner: London ✓ (business hours), Dubai ✓, Tokyo ✗ (3 am — outside business hours)

How day-boundary crossings work

When a conversion crosses midnight, the date changes. Tokyo is 13 hours ahead of EDT, so a 2 pm Tuesday in New York is 3 am Wednesday in Tokyo. The converter always shows the full date so you know whether the meeting is on the same calendar day.

Understanding Time Zone Converter — World Clock & Meeting Planner

How UTC Offsets and DST Work Together

Every time zone is defined by its offset from Coordinated Universal Time (UTC) — the global reference clock that replaced Greenwich Mean Time (GMT) in 1972. A zone like US Eastern Time has a standard offset of UTC−5 in winter and UTC−4 in summer (Daylight Saving Time). When DST is in effect, clocks are pushed forward by one hour so that sunset falls later in the evening.

Not all regions observe DST. Arizona (US), most of Africa, China, Japan, India, and much of Asia stay on a fixed offset year-round. This means the difference between two zones can change by an hour or two depending on the time of year — which is exactly why automated tools are more reliable than manual arithmetic.

The IANA Time Zone Database

Modern operating systems and browsers use the IANA Time Zone Database(also called the Olson database) to track every zone's current offset, historical changes, and future DST transitions. Each zone has a unique identifier in the format Continent/City — for example, America/New_York, Europe/Paris, or Asia/Kolkata. This calculator uses these identifiers directly through the JavaScript Intl.DateTimeFormat API, which is built into every modern browser.

Why Time Zone Conversion Trips People Up

›Day boundary crossings — adding 13 hours to 2 pm on Tuesday gives 3 am on Wednesday. The date changes, which matters for scheduling.
›Half-hour and quarter-hour offsets — India (UTC+5:30), Nepal (UTC+5:45), and Newfoundland (UTC−3:30) are not on whole-hour boundaries, so simple addition by whole hours fails.
›DST transitions don't happen simultaneously — the US and Europe change their clocks on different Sundays, creating a window each year where the offset between New York and London is different from normal.
›Southern hemisphere reversal — Australia and New Zealand have summer DST in November–March, opposite to the Northern Hemisphere.

Tips for International Meeting Planning

›The overlap between US Eastern and Europe (London, Paris, Berlin) is roughly 2 pm–5 pm ET / 7–10 pm CET — a practical window for transatlantic calls.
›Asia-Pacific to US meetings are particularly hard: a 9 am Singapore call is 9 pm the previous day in New York.
›Use the Meeting Planner feature to scan the overlap of business hours between zones rather than doing the arithmetic manually.
›Always confirm the UTC offset on the actual meeting day — changes near DST transitions can shift an offset by an hour.

A note on abbreviations like EST, PST, and IST

Abbreviations like EST, IST, or CST are ambiguous — IST can mean India Standard Time, Irish Standard Time, or Israel Standard Time. This calculator always shows the full IANA identifier alongside the abbreviation so there is no ambiguity.

Frequently Asked Questions

How does the converter handle Daylight Saving Time?

DST is handled automatically. The converter passes a specific date to the Intl.DateTimeFormat API with the IANA timezone string (e.g. America/New_York). The browser looks up the correct offset for that exact date — whether DST is active or not — and formats the time accordingly.

›No manual offset adjustments needed
›Handles transitions that happen mid-day correctly
›Works for historical and future dates within the IANA database
›Shows the actual UTC offset in use (e.g. UTC−4 vs UTC−5 for New York)

What is the difference between UTC, GMT, and a UTC offset?

›UTC — the international standard time reference, based on atomic clocks
›GMT — the historical reference based on the Greenwich meridian; effectively the same as UTC+0 for everyday purposes
›UTC offset — how many hours/minutes a zone is ahead (+) or behind (−) UTC
›Example: India Standard Time = UTC+5:30, meaning 5 hours and 30 minutes ahead of UTC

Why does my conversion show a different date in the target timezone?

This is expected — it means the conversion crossed midnight in the target timezone.

›New York 10 pm → Tokyo: add 13 hours → next day 11 am
›London 1 am → Los Angeles: subtract 8 hours → previous day 5 pm
›The converter shows the full date for each target so you always know the calendar day
›This is especially important for overnight flights, event scheduling, and deadlines

How does the Meeting Planner feature work?

›Green — the converted time falls within 9 am–5 pm in the target zone (good for meetings)
›Yellow — partial overlap: the time is near the edge of business hours in the target zone
›Red — the converted time falls outside 9 am–5 pm in the target zone (early morning or evening)
›Use this to quickly find the window where all participants are in working hours

Why do some countries have half-hour or quarter-hour UTC offsets?

›India Standard Time: UTC+5:30 — set to approximate solar noon for the subcontinent
›Nepal Standard Time: UTC+5:45 — set 15 minutes ahead of India to differentiate from a larger neighbour
›Iran Standard Time: UTC+3:30 (UTC+4:30 in summer)
›Newfoundland Standard Time: UTC−3:30

This is why simple hourly addition breaks down — always use an IANA-aware tool.